Field of the Invention
The present invention is generally directed toward a rapid-closure gate-type isolation valve. The gate valve comprises one or more integrated reservoirs for holding a pressurized gas that effects operation of the valve. The isolation valve further includes an actuator assembly responsible for initiating operation of the valve. In particular embodiments, the isolation valve operates without employing a pyrotechnic device.
Description of the Prior Art
Isolation valves, including gate-type valves, have been used to prevent propagation of hazardous conditions, such as fires and explosions, within various types of process equipment. As many hazardous conditions tend to propagate very quickly, rapid closure of valves is important to the successful isolation of vulnerable process equipment. A number of valve designs have been proposed which effect rapid closing and corresponding isolation of process apparatus.
U.S. Pat. No. 6,131,594 to Staggs et al. is directed toward an isolation gate valve. A valve actuator is provided which includes a gas-generating cartridge unit which, upon actuation, generates a charge of high pressure subsonic gas for shifting the gate member at a velocity of about 0.2 to about 0.33 in/msec. Essentially, the gas-generating cartridge contains a solid propellant that is combusted upon actuation of the valve. The gas generated by combustion of the solid propellant acts upon a piston to effect valve closure.
U.S. Pat. No. 5,362,028 to Jacobs is directed to a high-speed gate valve that is actuated by an explosive squib. Upon detection of a system abnormality, the squib explodes, which permits discharge of pressured gas from a bottle into a cylinder. Increased pressure within the cylinder forces the piston and its rod outwardly thereby moving the gate plate into a closed position.
The pyrotechnics used in these types of valves are heavily regulated, and thus the transport of such valves from the manufacturer to the customer can be very difficult, if such is even permitted by a particular jurisdiction.
U.S. Pat. No. 4,051,676 to Ledeen et al. is directed to an emergency hydraulic ram valve actuator and includes a cylinder having a piston that may be connected to a gate valve. Upon actuation of a poppet valve pressurized fluid is supplied from a pair of accumulators into a cylinder moving a piston which closes the valve. The Leeden et al. actuator comprises a number of redundancies so that the valve may still operate even though it may be damaged or partially disabled. Such systems greatly increase the complexity and bulk of the valve, which may render it unsuitable for installation in tight confines, which are often encountered in certain plants.